1. Field of the Invention
The present invention relates to new cure accelerators for anaerobic curable compositions. These anaerobic cure accelerators are generally sulfonimide derivatives and sulfonamide derivatives.
2. Brief Description of Related Technology
Anaerobic adhesive compositions generally are well-known. See e.g., R. D. Rich, “Anaerobic Adhesives” in Handbook of Adhesive Technology, 29, 467-79, A. Pizzi and K. L. Mittal, eds., Marcel Dekker, Inc., New York (1994), and references cited therein. Their uses are legion and new applications continue to be developed.
Conventional anaerobic adhesives ordinarily include a free-radically polymerizable acrylate ester monomer, together with a peroxy initiator and an inhibitor component. Oftentimes, such anaerobic adhesive compositions also contain accelerator components to increase the speed with which the composition cures.
Desirable anaerobic cure-inducing compositions to induce and accelerate cure may include saccharin, toluidines, such as N,N-diethyl-p-toluidine (“DE-p-T”) and N,N-dimethyl-o-toluidine (“DM-o-T”), acetyl phenylhydrazine (“APH”), maleic acid (“MA”), and quinones, such as napthaquinone and anthraquinone. See e.g., U.S. Pat. Nos. 3,218,305 (Krieble), 4,180,640 (Melody), 4,287,330 (Rich) and 4,321,349 (Rich).
Saccharin and APH have been used as standard cure accelerator components in anaerobic adhesive cure systems since the inception of the technology, and has been well studied in that connection. Hitherto, it was believed that the nitrogen-hydrogen bond off the heterocycle ring was necessary to achieve performance under anaerobic conditions, as early studies substituting the hydrogen with an alkyl group proved to be ineffective. See F. J. Boerio et al., “Surface-Enhanced Raman Scattering from Model Acrylic Adhesive Systems”, Langmuir, 6, 721-27 (1990), in which it is stated “[t]hese salts [of saccharin] are thought to be important factors in the curing reaction of the adhesive.”
And while anaerobic curable compositions having cure components including saccharin, DE-p-T and cumene hydroperoxide (“CHP”) display good performance on metal substrates, such compositions do not display as impressive performance on glass substrates. Thus, there exists a specific need to tailor anaerobic curable compositions to perform well on such substrates.
Recently, Henkel Corporation was granted U.S. Pat. No. 6,835,762 (Klemarczyk), which defines an invention directed to an anaerobic curable composition, comprising:                (a) a (meth)acrylate component;        (b) an anaerobic cure-inducing composition; and        (c) an anaerobic cure accelerator compound having the linkage —C(═O)—NH—NH— and an organic acid group on the same molecule. The composition is substantially free of acetyl phenyl hydrazine and maleic acid, and the anaerobic cure accelerator compound excludes 1-(2-carboxyacryloyl)-2-phenylhydrazine.        
There continues to be an on-going desire to find alternative technologies for accelerating the cure of anaerobic curable compositions, to differentiate existing products and provide supply assurances in the event of shortages or cessation of supply of raw materials. Accordingly, it would be desirable to identify new materials, which function as accelerators in the cure of anaerobic curable compositions.